Feasibility of motion-corrected planar projection imaging of single photon emitters: A phantom study

The kinetics of single photon emitting macromolecules (e.g. antibodies) are typically slower than small molecules, necessitating long or repeat acquisitions. We previously proposed the use of motion tracking and limited angle tomographic reconstruction to characterise tracer kinetics over extended periods in awake rodents. In this study, we explored this approach by imaging a contrast phantom, moved with 6 degrees of freedom, using a prototype preclinical SPECT scanner with parallel-hole collimation and a fixed detector located at 0 and 90 degrees. The position of the phantom was tracked and data were acquired in list mode. Each event was motion-corrected and reconstructed using LM-MLEM. Planar projections were created by summing the reconstructed volume along the x-axis. Line profiles of the contrast phantom were compared for a planar reference projection and projections generated from the motion-free, motion-corrupted and motion-corrected reconstructions. Projections created from the motion-corrected agreed well with the planar reference projection of the stationary object and exhibited similar contrast. Whilst this initial study was limited to rigid motion, it demonstrates the feasibility of motion-corrected planar projections of a moving object.